ProgramNode(0...29)(
  [],
  StatementsNode(0...29)(
    [DefNode(0...29)(
       (4...5),
       nil,
       ParametersNode(6...12)(
         [RequiredParameterNode(6...7)(:x)],
         [],
         [],
         nil,
         [],
         ForwardingParameterNode(9...12)(),
         nil
       ),
       StatementsNode(15...24)(
         [CallNode(15...24)(
            nil,
            nil,
            (15...16),
            (16...17),
            ArgumentsNode(17...23)(
              [LocalVariableReadNode(17...18)(:x, 0),
               ForwardingArgumentsNode(20...23)()]
            ),
            (23...24),
            nil,
            0,
            "b"
          )]
       ),
       [:x, :"..."],
       (0...3),
       nil,
       (5...6),
       (12...13),
       nil,
       (26...29)
     )]
  )
)
